: One-third of the world population is infected with Mycobacterium tuberculosis and TB causes 3 million deaths per year. Those individuals infected with AIDS have an increased risk of developing active TB. The recent emergence of multi- drug resistant forms of TB further exacerbates the already difficult control of TB. Development of new drugs for the treatment of TB is an important goal in the international crusade against this disease. In search of novel drug targets, these investigators have generated mutants in M. smegmatis which are blocked in the production of mycothiol (MSH), a compound that may play a key role in protecting the organisms against the oxidative stress mechanisms normally used by the immune systems to destroy invading bacteria. In this research, the investigators will expand upon earlier studies by characterizing the genes responsible for the defects of MSH biosynthesis in the mutant bacteria. The results of these studies should facilitate the identification and production of enzymes that can potentially serve as targets for the development of new TB drugs.